In electronic film development, the developing negative is scanned at a certain time interval using infrared light so as not to fog the developing film and to see through antihalation layers. Color is derived from a silver image during development by taking advantage of the milkish opacity of unfixed silver halide to optically separate the three layers sensitive to blue, green, and red. Viewed from the top during development, the top layer is seen clearly, while the lower layers are substantially occluded by the milkish opacity of the top layer. Viewed from the rear during development, the back layer is seen, while the other layers are mostly occluded. Finally, viewed under transmitted light, the fraction of light that does penetrate all three layers is modulated by all, and so contains a view of all three. If the exposures of "front", "back", and "through" views were mapped directly to yellow, cyan and magenta dyes, a pastelized color image would result. However in digital development these three scans, "front", "back" and "through", are processed digitally using color space conversion to recover full color. Electronic film development is described in greater detail in U.S. Pat. No. 5,519,510, issued May 21, 1996 to Edgar.
Conversion of analog images into digital data, or scanning, has become widespread for a variety of uses, including storing, manipulating, transmitting and displaying or printing copies of the image. In order to convert a photographic image into a digital image, the film image frame is transported through a film scanning station, and illuminated in each scan line with a linear light beam of uniform, diffuse illumination, typically produced by a light integrating cavity or integrator. The light transmitted through the illuminated scan line of the image frame is focused by a lens system on a CCD-array image detector which typically produces three primary color light intensity signals for each image pixel that are digitized and stored. Film scanners take a variety of forms and the various common aspects of film image frame digitizing, particularly line illumination and linear CCD array-based digitizers, are described in greater detail in U.S. Pat. No. 5,155,596.
In electronic film development, developer can be applied to the film substrate using a developer pod applied as a viscous fluid under a clear cover film with rollers as more fully described in the aforementioned Edgar et al. patent. Methods of application of developer to film are common knowledge in film development generally, and include sprays, washes, direct dunking, reel dunking, and tank immersion. In one example, developer is delivered through spray pipes which maintain a curtain of developer which cascades over the film. The run-off of excess developer may then be recirculated through the spray pipes for use in the development of other parts of the film. This process utilizes the traditional "wash" method which is followed by a rinse.
In another method of developer application, a film unit passes between two rollers and the force from the rollers ruptures a pod containing a processing fluid. The rollers then proceed to spread the processing fluid along the length of the film which results in the development of the film.
Despite the substantial advantages of electronic film development over conventional film development, which include reduced cost, smaller system size, and minimization of chemical handling, electronic film development is not in common use. One reason is that developer application as disclosed in U.S. Pat. No. 5,519,510 was unreliable and inconsistent in large scale use. Thus, methods and an apparatus for electronic film development which permit controlled application of developer or other chemical solutions without producing run-off are desirable.